1. Field
One embodiment of the invention relates to an information storage medium such as a recordable optical disc, a recording method, and a recording apparatus.
2. Description of the Related Art
In recent years, a digital versatile disc (DVD) has been practically used as a large-capacity optical disc. As a recordable DVD, a recordable DVD-R, a rewritable DVD-RW, and a DVD-RAM have been standardized. Once information is recorded on a recordable disc DVD-R, a recorded area cannot be rewritten. A conventional recordable DVD-R includes a power calibration area (PCA), a recording management area (RMA), and a data recording area (DA) in which an actual recording process is executed from the inner circumference side (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2002-245625 (paragraphs 0041 to 0052, FIG. 1)).
Furthermore, the data recording area DA includes a lead-in area in which recording parameter information and the like to be read when recording data is reproduced from a data area, a data area in which the recording data is recorded, and a lead-out area in which end information or the like to be read when reproducing of the recording data recorded in the data area is ended is recorded. The lead-in area is an area in which recording parameter information or the like is recorded before data is recorded in the data area. The lead-out area is an area in which end information is recorded before recording of recording data on an entire DVD is completed. The capacity of each area is predetermined and unchangeable.
When information is recorded on such a DVD (recording is performed from the inner circumference side of the data area), test recording is performed in the PCA area first. In this test recording, because the characteristics of optical discs of the same type vary depending on manufacturers and because of temperatures of a use environment, an operational environment of a laser, and the like, an optimal recording waveforms vary. Therefore, parameters (intensities, pulse widths, and the like) of the recording waveforms used when information is recorded on the optical disc are adjusted by a result of the test recording.
Thereafter, management information and user data are recorded in the RMA area and the data area, respectively. The management information includes information or the like representing a specific recorded area (record-end position) in the data area. Depending on the progress of recording of user data, the management information is updated into the latest management information. Since the part cannot be rewritten on the recordable DVD once information is recorded, a remaining capacity of the RMA area decreases each time the management information is updated. Depending on a method of updating management information, before recording in the entire area of the data area is completed, the RMA area may not have any more unrecorded areas. When the RMA area does not have an unrecorded area, the management information cannot be updated. Therefore, a recording operation for the data area must be stopped.
On the other hand, in the DVD device described above, a recording waveform changes. Depending on a recording position on a disc, an optimum recording waveform changes due to a change in temperature or aging. In order to adjust the recording waveform depending on these changes, in the DVD device, test recording is performed in the PCA area to adjust parameters of the recording waveform. Like the updating of the management information, each time the test recording is performed, the remaining capacity of the PCA area decreases. Depending on ways of executing the test recording, the PCA area may not have any more unrecorded areas before recording in the entire area of the data area is completed. When there is no unrecorded area in the PCA area, a recording operation must be stopped, or the user data and the management information must be recorded without adjusting the recording waveform. Sufficiently reliable information cannot be reproduced from a part on which the information is recorded with an unadjusted recording waveform.
In order to prevent shortage of the RMA area or shortage of the PCA area, the large capacity of the RMA area or the PCA area may be reserved in advance. However, in this case, the capacity of the data area reduces. As a result, even though the unrecorded areas in the RMA area and the PCA area sufficiently remain, the capacity of the data area may not be large enough.
On the other hand, in order to increase a recording capacity, the standards of a next-generation DVD in which the diameter of a beam spot is narrowed by shortening the wavelength of a laser beam or increasing a numerical aperture NA to increase a recording capacity have been proposed. As a method of increasing a recording capacity, a single-sided multilayer storage medium is also proposed. That is, in addition to the narrowing down of the beam spot, a plurality of recording layers are formed on one side of a disc, an objective lens is moved in an optical-axis direction to focus the beam on the respective layers, so that recording and reproducing can be performed on the respective recording layers (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2004-206849 (paragraphs 0036 to 0041, FIG. 1)).
The single-sided multilayer storage medium has a problem called interlayer crosstalk which does not occur in a single-sided single-layer storage medium. For descriptive simplification, a dual layer medium will be exemplified. On a single-sided dual layer storage medium, a laser beam is focused on the respective layers from a single read surface. A layer which is close to the read surface is called layer 0, and a layer which is far from the read surface is called layer 1. When the beam is focused on each layer, some laser beam is irradiated on a layer except for a target layer. Therefore, a reflected beam from the layer except for the target layer is mixed with a reproducing signal at the time of reproducing, interlayer crosstalk occurs. The interlayer crosstalk causes a problem not only at the time of reproducing but also at the time of recording.